Hydrazine is a highly toxic, yet common component of hypergolic rocket fuel that is used by both NASA Shuttle and DOD missile systems and used routinely in industrial processes. Hydrazine, monomethylhydrazine, and unsymmetric hydrazine are routinely used and often collectively referred to as the hydrazines (HZ). As a routinely-used toxic chemical, permissible exposure levels (PEL) are highly regulated. Although the Occupational Safety and Health Administration (OSHA) PEL level for hydrazine is 1 ppm, American Conference of Industrial Hygienists (ACGIH) has recommended that the level be lowered to 10 ppb. The administrative levels at the Kennedy Space Center follow the more stringent maximum exposure limit of 10 ppb recommended by ACGIH. Thus, personal exposure and workplace monitoring is required to assure worker safety and workplace compliance to government standards.
There are numerous existing technologies for measuring HZ, including electrochemical, metal oxide, photo-ionization detector (PID), mass spectrometer (MS), and Infrared (IR) sensors. In general, electronic monitors adapted to measure hydrazine vapors often tend to be expensive, require considerable manual maintenance, are plagued with responses from numerous interferants and/or lack of stability or sensitivity or selectivity (e.g., see “Electronic Nose for Space Program Applications” Rebecca C. Young, William J. Buttner, Bruce E. Linnell, and Rajeshuni Ramesham, Sensors and Actuators 93 (2003) 7-16). Passive colorimetric devices also exist for detecting hydrazine vapors. However, these devices either require a bulky and power hungry optical reader for triggering an alarm or require that operators get within eyesight of the indicator (typically less than 2 meters), which means operators can be exposed to the vapor while reading the indicator or must be dressed in cumbersome expensive protective equipment to read the monitor.
Accordingly, there is a need for improved chemical sensors devices.